Optical information recording medium and composition for optical information recording film

ABSTRACT

An optical information recording medium is here disclosed which comprises a transparent substrate, a recording layer comprising an organic dyestuff on which information can be written by a laser beam, a reflective layer and a protective layer formed in this order on the substrate, the aforesaid optical information recording medium being characterized by containing a pit-edge control agent for the formation of recording pits, particularly a dyestuff thermal decomposition accelerator in the recording layer. By the addition of the pit-edge control agent, deviation properties and jitter properties can be remarkably improved, whereby a CD-R medium having a low error rate and good recording properties can be provided. In consequence, stable compatibility with a commercial CD player can be secured.

This is a division, of application Ser. No. 08/159,585 filed on Dec. 1,1993, now U.S. Pat. No. 5,492,744, allowed Aug. 24, 1995.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to an optical information recordingmedium, a composition for an optical information recording film, and amethod for preparing the optical information recording medium. Morespecifically, it relates to a writing once optical information recordingmedium having compatibility with a compact disc, a composition for itsrecording film, and a method for preparing the recording film.

(ii) Description of the Prior Art

Some of optical information recording media using a laser beam havealready been put to practical use as large capacity data memories.

In particular, compact discs (CDs) and CD-ROMs have been utilized asrapid access digital recording media having large capacity to memorizevoices, images, code data and the like, and they have spread in markets.However, all of them are read only memories, and so in these media,anything cannot be recorded. Hence, a write-once optical recordingmedium is desired in which recording/editing can be optionally done by auser and which has compatibility with CDs and CD-ROM players largelyspread in the markets.

Thus, there have been suggested and developed the optical recordingmedia, i.e., CD-R media in which the recording can be carried out inaccordance with compact disc (CD) standards [Nikkei Electronics, No.465, p. 107, Jan. 23, 1989; and Optical Data Storage Technical DigestSeries, Vol. 1, p. 45 (1989)]. The CD-R medium is formed by laminating arecording layer, a reflective layer and a protective layer in this orderon a transparent resin substrate. When the recording layer is irradiatedwith a laser, a pit is formed in the recording layer, and the detectionof a signal is carried out by a reflectance change at this site. Thismedium has a single plate structure having a thickness of 1.2 mm so asto satisfy CD standards, and the pits having 9 kinds of length at aninterval of T in the range of from the shortest 3T pit length to thelongest 11T pit length (T=231.4 ns) are used in accordance with amodulation method of a CD system, i.e., an EFM (eight to fourteenmodulation) system. Therefore, in the CD-R medium, the pitscorresponding to the 9 kinds of predetermined length are formed by thelaser irradiation, and the pit length is reproduced by the detection ofthe thus formed pit edges.

In the recording system of the write-once optical information recordingmedium, particularly the CD-R medium, heat mode recording (thermalrecording) which has undergone light/heat conversion is usually employedas a practical level. Therefore, as the composition for the recordingfilm, there have been suggested low-melting metals, organic polymers andsome organic dyestuffs which give rise to a physical change or achemical change such as melting, vaporization, sublimation ordecomposition. Above all, the organic dyestuffs which have a low thermalconductivity, a low melting point or a low decomposition temperature arepreferable from the viewpoint of recording sensitivity. In addition,these organic dyestuffs are also preferable in point of optical design,because they can hold high reflectance for CD compatibility. Inconsequence, much attention has been mainly paid to cyanine dyestuffs,metal phthalocyanine dyestuffs, naphthoquinone and azo dyestuffs, andthe recording layers have been developed from these dyestuffs.

Heretofore, some examples have been disclosed in which the CD-R mediaare constituted of the organic dyestuffs.

Hamada et al. have suggested and disclosed a CD-R medium in which theoptical recording layer comprises a layer containing a cyanine dyestuffin Japanese Patent Application Laid-open No. 147286/1990. The mediumsystem has high reflectance and good recording sensitivity.

However, the present inventors have found that this suggested inventionhas some problems. That is, since the recording layer comprises thecyanine dyestuff, error rate and jitter properties deterioratenoticeably under a high-temperature and high-humidity environment, andlight resistance also declines, and so when data communication is oftencarried out with a CD, the reliability of the medium for a long time ispoor. As more serious troubles, in EFM pit length recording, theformation stability of particularly the 3T pit edge is not always good,and problems of the jitter properties and the error rate take place attimes.

Japanese Patent Application Laid-open No. 215466/1991 discloses a CD-Rmedium in which the optical recording layer comprises a phthalocyaninedyestuff having a specific substituent. The recording film comprisingthis dyestuff is excellent in light resistance, humidity resistance andheat resistance, so that the optical recording medium having goodbalance between reflectance and recording sensitivity can be provided.In this dyestuff system, however, we have elucidated the feature that inthe EFM pit length recording, particularly the pit of 3pit length isformed more largely than in the prepits of the commercial CD and CD-ROM,and we have found that defective playback on the commercial orconventional CD player cannot be completely avoided owing to thisfeature of the pit edge.

On the other hand, with regard to the optical information recordingmedia, some examples have been disclosed in which a certain kind ofadditive is added to the recording layer to improve the characteristicsof this layer.

In Japanese Patent Application Laid-open No. 86787/1980, the improvementof recording sensitivity is intended, and a light absorber for arecording laser beam is added to the recording layer comprising anorganic dyestuff or a resin to improve a light/heat conversionefficiency, whereby permitting the formation of the recording pits evenby the laser irradiation of lower power. This light absorber itself doesnot have any influence on the recording threshold performances of theorganic dyestuff or the resin having a recording function, for example,the thermal decomposition temperature of the organic dyestuff, and thus,substantially, the stability of the recording pits themselves formed bythe heat mode recording is not always good. Additionally, in opticalinformation recording media such as the CD-R medium in which theretention of the high reflectance for the CD compatibility is required,the deterioration of the reflectance which is inevitably caused by theaddition of the light absorbent is not preferable.

Furthermore, Japanese Patent Application Laid-open Nos. 16888/1983,62839/1983 and 92448/1984 disclose examples in which the recordingsensitivity is mainly improved by adding an additive havingself-oxidizing properties, for example, a nitro-based compound (such asnitrocellulose) to the organic dyestuff layer which is the recordinglayer. It has been confirmed that in this nitro-based system, the heatgenerated at the exothermic self-oxidizing decomposition of the additivefunctions as an effective heat source on recording, and the influence ofthe organic dyestuff itself having the recording function on therecording threshold properties and decomposition properties is observedsometimes. However, in this nitro-based system, the formation of thepits inevitably involves the rapid heat generation at the time of theoxidizing decomposition, and so the uniformity of the formed recordingpit-edges is not always good. From experiments in which nitrocelluloseis added, the present inventors have observed that particularly in thecase that the pit length recording for the CD compatibility is carriedout in the EFM system, the noticeable deterioration of signal qualitiessuch as jitter properties is not avoidable.

In Japanese Patent Application Laid-open No. 23-9943/1986, Nanba et al.disclose the improvement of the light resistance of an optical recordinglayer by the use of the mixture system of an indolenine cyanine dyestuffand a dithiole transition metal complex, and additionally, in JapanesePatent Application Laid-open No. 25493/1992, they also describe theapplication of a mixture film comprising a cyanine dyestuff and theabove-mentioned dithiole transition metal complex in a CD-R medium. Inthis system, the durability, particularly the light deterioration of therecording layer which is considered a problem can be improved to someextent without impairing the recording properties of the cyaninedyestuff. However, in this technique, it has been confirmed that thedithiole metal complex functions, for the improvement of the durabilityof the medium, as an effective quencher for singlet oxygen which isconsidered to be the main cause of the light deterioration of thecyanine dyestuff, but the effect and improvement of characteristics inthe pit length recording and the pit-edge detection as neitherrecognized nor referred to.

Other examples have been present in which the characteristics of theoptical information recording medium are improved by an intramolecularor an intermolecular function of the organic dyestuff and a certainmetal compound, but most of them are mainly concerned with theimprovement of the durability of the above-mentioned recording film orthe matching of the recording film with a recording laser wavelength inan absorptive section. Therefore, the effect of the used organicdyestuff on the recording threshold properties and the like is neitherexpected nor referred to.

As stated above, in the optical information recording media which havebeen heretofore developed, the control of the pit-edge is not alwayssufficient, and for this reason, the application of the media to the pitlength recording is particularly difficult. Specifically, in the CD-Rmedium which is one typical example of the conventional media, thecompatibility with the CD of the read only memory is not alwayssufficient, and in the playback on the prevalent commercial CD player,the CD-R medium gives rise to a problem at times.

The present inventors have analyzed and investigated this problem, andas a result, they have found that the jitter components increase owingto the poor control of the pit-edge formed at the time of the laser beamirradiation, and that particularly in the pit length recording, therecording pits/lands are formed, deviating from a predetermined pitlength or a pit interval length (hereinafter referred to as “landlength”). This means the deviation from the pit standard length, and soit will be referred to “deviation properties.” Thus, it has been foundthat in the process of data playback from the recording pits, the readerror of a signal length tends to occur, and property deterioration suchas the increase of the error rate takes place. In addition, it has beenalso found that this deterioration behavior is very liable to occur atthe time of the formation of the pit length/land length which is smallerthan the diameter of the irradiated laser beam.

Here, selecting the CD-R medium as an example, the shortest 3T pitlength (0.83-0.97 micron) and the shortest 3T land length are requiredto be stably formed, avoiding light interference and heat interferencein the recording film, in accordance with the CD recording system (EFMsystem) by the irradiation of laser beam having an effective radius ofabout 1 micron (usually by the use of a semiconductor LD in a nearinfrared region). However, in the conventional recording film design,this pit-edge control is very difficult. Therefore, particularly theformed 3T pits are excessively larger or smaller than the 3T prepitlength of the commercial CD (in which compatibility with the CD playeris sufficiently secured), and the deviation properties are poor and thejitter value is also high, so that errors are often made. In the worstcase, it has been found that the problem of the defective playback takesplace in the CD player.

SUMMARY OF THE INVENTION

The present inventors have intensively conducted research to solve theabove-mentioned problems, and as a result, they have found that theabove-mentioned deviation properties and jitter properties can beremarkably improved by adding a kind of pit-edge control agent to anorganic dyestuff which is used as a recording layer.

The present invention is directed to an optical information recordingmedium which comprises a transparent substrate, a recording layercomprising an organic dyestuff on which information can be written by alaser beam, a reflective layer and a protective layer formed in thisorder on the substrate, the aforesaid optical information recordingmedium containing a pit-edge control agent for the formation ofrecording pits in the recording layer,

-   -   preferably containing a thermal decomposition accelerator for        the dyestuff as the pit-edge control agent in the recording        layer,    -   further preferably containing a metallic compound as the thermal        decomposition accelerator in the recording layer,    -   further preferably containing a metallic compound having        substantially no absorption at wavelength of a recording laser        beam, and    -   further preferably, the recording layer comprising the organic        dyestuff is formed by a coating method using a solvent for the        dyestuff, and the metallic compound having substantially no        absorption at the wavelength of a recording laser beam in        soluble in a solvent for the organic dyestuff.

Here, the present invention is directed to an optical informationrecording medium preferably containing a metallocene or its derivativeas the above-mentioned metallic compound,

-   -   preferably containing a β-diketonato metal complex represented        by the following formula (1) as the metallic compound:        wherein each of the substituents X, Y and Z is independently a        hydrogen atom, a halogen atom, R¹, OR², SR³, COOR⁴, COONR⁵R⁶,        SiR⁷R⁸R⁹ or NR¹⁰R¹¹, and M is a metal having a valency of n        (wherein R¹ is an unsubstituted or a substituted alkyl group,        aryl group or unsaturated alkyl group, and each of R², R³, R⁴,        R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰ or R¹¹ is a hydrogen atom, an        unsubstituted or a substituted alkyl group, aryl group or        unsaturated alkyl group), and    -   preferably containing an anti-knocking agent as the metallic        compound.

Furthermore, the present invention is directed to an optical informationrecording medium using a phthalocyanine compound as the organicdyestuff, and

-   -   preferably using a halogenated phthalocyanine as the dyestuff.

Moreover, the present invention covers a composition for an opticalinformation recording medium comprising an organic dyestuff and theabove-mentioned pit-edge control agent,

-   -   a composition for an optical information recording medium more        preferably comprising a phthalocyanine compound as an organic        dyestuff and the above-mentioned pit-edge control agent, and    -   a composition for an optical information recording film more        preferably comprising a halogenated phthalocyanine compound as        an organic dyestuff and the above-mentioned pit-edge control        agent.

In addition, the present invention also covers a method for preparing anoptical information recording medium which comprises the steps of:

-   -   dissolving the above-mentioned composition in a solvent to form        a solution, and    -   coating thus obtained solution on a transparent substrate,        thereby forming a recording layer comprising an organic dyestuff        and the above-mentioned pit-edge control agent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptional view regarding the definition of a pit-edge.

FIG. 2 is a recording laser irradiation profile.

FIG. 3 is a conceptional view regarding the definition of a recordingthreshold level and a pit-edge.

FIG. 4 is a conceptional view of a deviation (Δ) and a jitter (σ).

FIG. 5 is a heat reduction curve by a TG analysis.

FIG. 6 is a conceptional view regarding the definition of a thermaldecomposition accelerator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Here, technical terms used in the present invention, will be defined.

Referring to FIG. 1, in the present invention, a recording pit 1 formedby laser irradiation is read out by an optical head installed on a CDplayer or the like as a signal (HF signal) (2) of a reflectance changeshown. Binary-coded signal 4 is obtained via data slice circuit (whichis represented by a slice level 3 in FIG. 1). A pit-edge 5 is defined asthe position where an inversion of binary-coded signal takes place. Thisdata slice circuit is described in detail in “Illustrated Compact DiscBook (second edition)” (written by Nakajima and Ogawa, and published byOhm Co., Ltd.) and the like.

A pit-edge control can be established if a distance between thepit-edges is given with a small deviation (jitter) and good linearity inthe range of from the shortest pit length (or land length) to thelongest pit length (or land length). This also means that the uniformityof the shape of the formed pit is apparently good and that the shape ofthe formed pit-edge is forwardly and backwardly symmetrical to thecenter of the pit and the pit-edge does not have strain and the likewith sufficiently slight degree of deformation in a substrate, arecording layer and/or a reflective layer. In order to achieve highdensity, it is required to form a pit or pits having a pit edge lengthequal to or smaller than the spot diameter of the recording laser. Insuch a case, a good linearity is not given on the basis of a recordingthreshold level (a pit formation energy level) because in the shortestpit, the peak of the laser irradiation energy is not saturated yet,while the other longer pit/land is being saturated. FIG. 2 shows a laserirradiation profile to a laser input of nT by an EFM system (n=3, 4, 5,6 or 11; calculated value). FIG. 3 shows the relation between a laserirradiation profile and the recording energy threshold level. Recordingis made with the energy greater than this threshold level. Here,reference numerals 6, 7, 8, 9 and 10 in FIGS. 2 and 3 are the laserirradiation profiles of 3T, 4T, 5T, 6T and 11T, and reference numeral 11is a recording threshold level. Here, it is considered that the formedpit length can be supposed from a point where this recording thresholdlevel 11 intersects with the laser irradiation profile, and when the pitis formed in proportional to each laser input length, it can be definedthat the linearity is good. As elucidated in the case of the thresholdlevel 11 in FIG. 3, the present inventors have presumed that mainly inthe formation of the shortest pit-edge which is smaller than thediameter of the beam, the jitter component is large, and so the controlof the linearity is difficult. Thus, in order to form the pit-edgehaving the standard length as the good linearity, it has been consideredthat the recording threshold level of the recording film is ratherrequired to be properly changed and regulated to secure the goodlinearity from the shortest pit. In the case of the threshold level 12shown in FIG. 3, the formed pit length can be taken out at 3:4:5:6:11 asshown by reference numerals 13, 14, 15, 16 and 17 in correspondence withthe laser input of 3T, 4T, 5T, 6T and 11T and consequently, theabove-mentioned linearity is well established.

The pit-edge control agent which is referred to in the present inventioncan be defined as an additive which has an influence on the recordingthreshold level of the recording layer and makes change the same toachieve the stable formation of the shortest pit length, therebypermitting the good pit-edge control.

This pit-edge controllability can be determined by directly observingthe shape of the formed pit-edge by the use of an optical microscope,SEM, STM or the like. Alternatively, as a rather simple and practicalprocedure, the pit-edge controllability can be determined by playingback the formed recording pit line by the above-mentioned optical head,binary-coding by a data slice circuit, and then evaluating jitterproperties and deviation properties by a time interval analyzer. Ingeneral, the detected frequency distribution of the signal pit lengthcorresponding to a standard value 1₀ (18 in FIG. 4) is as shown in FIG.4. If the average value of a detected pit length (19 in FIG. 4) is 1,the absolute value Δ (={1₀−1}) (20 in FIG. 4) of a difference from thestandard value 1₀ is evaluated to be the deviation properties, and anunevenness σ (standard deviation) of its distribution (21 in FIG. 4) isevaluated to be the jitter properties. In particular, the deviation andthe jitter of the shortest pit length and the shortest land length inthe applied modulation system are represented by appendages _(p) and ₁,respectively, and the following parameters s_(p) and s_(l) areintroduced as the pit-edge controllability:s_(p)=Δ_(p)+2 σ_(p)s_(l)=Δ_(l)+2 σ₁

A certain kind of additive is called a pit-edge control agent which candecrease both s_(p) and s_(l).

Furthermore, in the thermal decomposition accelerator for a dyestuff asthe pit-edge control agent of the present invention, thermaldecomposition of dyestuff can be evaluated by the thermogravimetricanalyst (TG analysis).

Using, for example, a multipurpose thermal analytical device in whichthe balance mechanism of a horizontal type differential system isemployed, a thermal reduction curve shown in FIG. 5 is obtained. In FIG.5, a temperature of a point 22 at which the weight of the dyestuff isreduced to 80% of the initial weight of the dyestuff is defined as athermal decomposition starting temperature 23.

Next, in the case that the thermal decomposition starting temperature ofthe dyestuff moves toward a lower temperature side (24 in FIG. 6) thanthe thermal decomposition starting temperature of the single dyestuff asshown in FIG. 6, this additive can be defined as the thermaldecomposition accelerator for a dyestuff. Here, it is desirable that thethermal decomposition starting temperature moves toward the lowertemperature side as much as 10° C. or more, preferably 25° C. or more.

Now, the constitution of an optical information recording medium of thepresent invention and a composition for an optical information recordinglayer will be described in detail.

As the material of the above-mentioned transparent substrate, any onecan be used, so long as it is a material which can substantiallytransmit a laser beam for use in recording and which can be used in ausual optical recording medium. Examples of the transparent substrateinclude polymer materials such as a polycarbonate resin, an acrylicresin, a polystyrene resin, a vinyl chloride resin, an epoxy resin, apolyester resin and an amorphous polyolefin as well as inorganicmaterials such as glass. The substrate may have pregrooves or prepits,if necessary. The above-mentioned material can be molded by injectionmolding or a 2P method and then used as the substrate for the opticalinformation recording medium. Furthermore, the laser beam incident sideof the substrate may be coated with an inorganic thin film or a thinfilm comprising a dyestuff or a resin, if necessary, and this film alsointends to prevent rubbish or dust from adhering thereto and to protectthe substrate from a scratch.

No particular restriction is put on an optical recording layer, so longas it is an organic dyestuff having absorption mainly in the wavelengthregion of the laser beam for the recording and involving physical andchemical deformation, modification, decomposition, melting and foamingby the irradiation of the laser beam having a certain energy or morewith optical/thermal conversion. For example, the following organicdyestuffs can be enumerated as the materials having an effectiverecording power.

That is, phthalocyanine dyestuffs, naphthalocyanine dyestuffs, cyaninedyestuffs, squarylium dyestuffs, pyrylium dyestuffs, thiopyryliumdyestuffs, azulenium dyestuffs, naphthoquinone dyestuffs, antbraquinonedyestuffs, indophenol dyestuffs, triphenylemthane dyestuffs, xanthenedyestuffs, indanthrene dyestuffs, indigo dyestuffs, thioindigodyestuffs, merocyanine dyestuffs, acridine dyestuffs, oxazine dyestuffsand azo dyestuffs.

Above all, the phthalocyanine dyestuffs and the naphthalocyaninedyestuffs are very preferable, because their noticeable lightresistance, humidity resistance and heat resistance have been confirmedand the design of an absorption band in the wavelength region of therecording laser is possible. Furthermore, as compared with other organicdyestuff systems, these dyestuffs are also desirable as the system inwhich the effect of the pit-edge controllability described herein,particularly the addition effect of the dyestuff thermal decompositionaccelerator is effectively exerted. The particularly preferablephthalocyanine organic dyestuffs are compositions mentioned in U.S. Pat.No. 5,124,067, U.S. Pat. No. 5,220,010, U.S. Pat. No. 5,024,926,EP-4960538, EP-513370 and EP-519419.

In addition, more preferable examples of the dyestuffs includehalogen-substituted phthalocyanine and naphthalocyanine dyestuffs, andhalogen compound-containing phthalocyanine and naphthalocyaninedyestuffs, and it has been confirmed that the effect of the presentinvention is further effectively exerted by adding the pit-edge controlagent mentioned herein, particularly the dyestuff thermal decompositionaccelerator. Probably, it can be presumed that the effective function ofthe dyestuff thermal decomposition accelerator is easily exerted via thehalogen introduced as a substituent or the halogen present in therecording film, but its definite mechanism is unknown.

As the halogenated phthalocyanine organic dyestuffs, compositionsmentioned in U.S. Pat. No. 5,124,067, U.S. Pat. No. 5,220,010 and thelike are particularly preferable. As the halogen atom for thesubstitution, bromine is particularly good. Moreover, the halogencompounds may be present in a mixed state in the recording film. Noparticular restriction is put on the halogen compound, so long as it hasgood solubility like the recording film and is excellent in workabilityand durability, but it is selected from halogenated alkyl compounds,halogenated aromatic compounds and halogenated olefin compounds. Inparticular, it has been confirmed that o-tetrahalogenated xylene and itsderivatives are preferable, because they can effectively increase thefunction of the dyestuff decomposition accelerator and can exert theeffect.

Of course, the organic dyestuffs mentioned above may be used singly orin the form of a mixture of two or more thereof. Furthermore, it is alsopossible to laminate two or more kinds of organic dyestuffs havingdifferent compositions.

On the other hand, no particular restriction is put on the pit-edgecontrol agent to be added, so long as it, when added, has an influenceon the recording threshold level of the recording film to reduce thepit-edge controllability s. In the case of the EFM system, in order toobtain the sufficient compatibility with the CD player in considerationof a data detection window width T/2 (=116 ns), it is preferable tosatisfy.s_(p)=<70 ns ands_(l)=<70 ns.

Additives which can effectively give the pit-edge control effect whenadded are substances capable of altering the physical properties of therecording layer on recording, and examples of these additives includethe thermal decomposition accelerator for the dyestuff, an oxidationaccelerator, a heat generation inhibitor, a melting point depressant, asurface active agent, a lubricant, a dispersant, a crosslinking agent, afoaming agent and an anti-foaming agent.

According to the detailed investigation by the present inventors, as aneffective physical parameter (recording threshold) which should be notedto more successfully achieve the pit-edge control, the thermaldecomposition temperature of the organic dyestuff layer is particularlyraised. Especially, in order to effectively reduce the edgecontrollabilities, the additive to be added to the recording layer isrequired to be an additive capable of causing the heat decomposition ofthe organic dyestuff used in the recording layer on a lower side.Therefore, it is preferable that the pit-edge control agent of thepresent invention is the dyestuff heat decomposition accelerator.Needless to say, in this system, it has been confirmed by theobservation of SEM or the like that the uniformity of the recordingpit-edge shape is very good. Here, no particular restriction is put onthe thermal decomposition accelerator for the dyestuff to be added, solong as the acceleration of the dyestuff thermal decomposition by thethermal decomposition accelerator for the dyestuff can be confirmed bythe above-mentioned TG analysis. Nevertheless, its preferable examplecan move the dyestuff thermal decomposition starting temperature as muchas 10° C. or more, preferably 25° C. or more on the lower temperatureside. Furthermore, the dyestuff molecule to be used and the dyestuffdecomposition accelerator molecule to be added may have a certainphysical or chemical interaction when mixed, so long as they do notdisturb the effect of the present invention. Of course, for the sake ofthis function, the dyestuff thermal decomposition acceleratorcomposition at the time of the addition may take either state of solidor liquid.

Here, as the thermal decomposition accelerator for the dyestuff which isexcellent in the deviation properties of the recording pit and which canparticularly satisfy the low jitter properties from the good pit shape,preferably are a series of metallic compounds whose very excellentfunctional effect can be confirmed. This metallic compound means asubstance constituting a compound in which an element defined as a metalelement in the periodic table is contained in the form of an atom, anion or a cluster. In particular, a preferable system in which the effectof the present invention can be effectively exerted is a morphology ofan organic metal compound, i.e., a ligand comprising a certain kind oforganic compound, or a compound having a bond to a metal atom or a metalion in the state of a pair of ions. For example, selecting an ironmetallic compound as an exemplary system for very effectively exertingthe effect of the present invention, examples of the metallic compoundwhich can be used in the present invention include fatty acid irons suchas iron formate, iron oxalate, iron laurate, iron naphthenate, ironstearate and iron butyrate; chelate coordination iron complexes such asacetylacetonato iron complex, phenanthroline iron complex, bispyridineiron complex, ethylenediamine, iron complex, ironethylenediaminetetraacetate complex, diethylenetrimaine iron complex,diethylene glycol dimethyl ether iron complex, diphosphino iron complexand dimethyl glyoxymato iron complex; inorganic iron complexes such ascyano iron complex and ammine iron complex; iron carbonyl complex; andbisyclopentadienyl iron complex (ferrocene). In addition, the ironmetallic compounds also include iron halides such as ferrous chloride,ferric chloride, ferrous bromide and ferric bromide; inorganic ironsalts such as iron nitrate and iron sulfate; and iron oxides.

Furthermore, the thermal decomposition accelerator for the organicdyestuff herein is preferably specified from the metallic compoundswhich do not have any absorption in the recording laser wavelengthregion to be used, and therefore it is also very large feature that thereflectance of the recording film does not deteriorate even when thethermal decomposition accelerator is mixed with the organic dyestuff. Itcan be here defined that the absorption is present when ε<10 mol⁻¹ cm⁻¹is satisfied in the noted wavelength region wherein ε is an opticalmolar extinction coefficient of the added substance.

Moreover, from the viewpoint of the process, the thermal decompositionaccelerator which is used herein for the organic dyestuff and has noabsorption in the laser wavelength region is preferably mixed with theorganic dyestuff and simultaneously molded into a film, and therefore itis preferable that the thermal decomposition accelerator is soluble in asolvent which can dissolve the organic dyestuff therein at the time ofthe film formation and which is excellent in workability. Incidentally,this dissolution can be here defined as that there can be attained asolubility of 0.2 g/l or more, preferably 1 g/l or more in the solventwhich is used to dissolve the organic dyestuff.

As the above-mentioned pit-edge control agent which is the metalliccompound, shows the particularly good dyestuff thermal decompositionacceleration effect, has no absorption in the laser wavelength region,is excellent in the solubility in the film formation solvent for theorganic dyestuff, and can effectively exert the effect of the presentinvention, there can be mentioned metallic compounds such as a series ofmetallocene compounds and their derivatives, a series of β-diketonatometal complexes and their derivatives, and metal-based anti-knockagents. In the system containing the added metal-based compound, thethermal decomposition starting temperature of the dyestuff can bedropped as much as about 25° C. or more, and the good pit-edge controlhas been confirmed. For example, at the time of the application of theEFM, the excessive extension or reduction of mainly 3T pit which hasbeen difficult to control in a conventional CD-R medium is successfullyinhibited, so that the deviation of the formed pits can be remarkablyimproved, and the jitter properties can also be improved.

Examples of the metallocene compound which permits the effectiveexertion of the effect of the present invention include Febiscyclopentadienyl complex (ferrocene), biscyclopentadienyl metalcomplexes of Ti, V, Mn, Cr, Co, Ni, Mo, Ru, Rh, Zr, Lu, W, Os and Ir. Ithas been confirmed that above all, ferrocene, ruthenocene, osmocene,nickelocene, titanocene and their derivatives, which are thermallystable, of course at ordinary temperature, during the laser irradiationand even at a relatively high temperature, are very excellent in thepit-edge controllability at the time of the laser recording, and theycan also remarkably improve the durability of the optical informationrecording medium comprising the composition.

The organic dyestuffs and the metallocene derivatives may be usedrespectively singly or in the form of a mixture of two or more thereof.If necessary, additive substances such as a binder can be suitablyadded. Of course, the metallocene compound to be used herein may have asubstituent or substituents, so long as it does not impair the effect ofthe above-mentioned invention. Examples of the acceptable substituentinclude alkyl groups having 1-10 caron atoms, acyl groups having 2-10carbon atoms, aryl groups having 6-10 carbon atoms, aryloyl groupshaving 7-10 carbon atoms, aldehyde groups having 1-10 carbon atoms,carboxyl groups having 1-10 carbon atoms, alkoxy groups having 1-10carbon atoms, amino groups having 0-10 carbon atoms, a hydroxyl group,halogen atoms and alkenyl groups having 2-10 carbon atoms. Above all,the metallocene compounds substituted by the alkyl group, the acyl groupor the benzoyl group are preferable from the viewpoints of solubilityand sublimation resistance.

Next, the effective β-diketonato metal complex is any of compoundsrepresented by the following formula (1)

wherein each of the substituents X, Y and Z is independently a hydrogenatom, a halogen atom, R¹, OR², SR³, COOR⁴, COONR⁵R⁶, SiR⁷R⁸R⁹ orNR¹⁰R¹¹, and M^(n+) is a metal having a valence of n (wherein R¹ is anunsubstituted or substituted alkyl group having 1-10 carbon atoms, suchas methyl, ethyl, propyl and butyl, aryl group having 6-10 carbon atomsor unsaturated alkyl group having 2-10 carbon atoms; each of R², R³, R⁴,R⁵, R⁶,R⁷, R⁸, R⁹, R¹⁰ or R¹¹ is a hydrogen atom, an unsubstituted orsubstituted alkyl group having 1-10 carbon atoms, aryl group having 6-10carbon atoms or unsaturated alkyl group having 2-10 carbon atoms).

In the above-mentioned formula, examples of M include transition metalsin the periods IV, V and VI such as Fe, Co, Cr, Ni, Ti, V, Mn, Cu, Zn,Zr, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, W, Re, Os, Ir, Pt and Pb; transitionmetal oxides such as VO and MoO; and typical elements such as Mg, Ca, Baand Al, As the β-diketonato metal complexes which can easily achieve thegood film formation, is excellent in the deviation properties of therecorded pits, and can satisfy the low jitter properties from aparticularly good pit shape, a serial of acetylacetonato compounds (eachof X and Y═CH₃, and Z is H) are very preferable, and in particular, theacac complexes of Cr, Co, Fe, Ni, V, VO, MoO and Zr can show theextremely good functional effect. Above all, the complexes containingCr, Co, V, Fe and Ni are the most preferable, because a general-purposeoptical information recording medium such as CD-R comprising any of suchcomplexes is very excellent in durability. Furthermore, if theimprovement of the solubility and the film formation properties isintended, each substituent of X, Y and Z is preferably an unsubstitutedor substituted alkyl group, aryl groups, alkoxyl group or a halogenatom.

Next, with regard to the anti-knock agent which is specified as thedyestuff thermal decomposition accelerator, an octane value described in“Fuel Handbook” (Corona Publishing Co. Ltd., 1974, pp. 267-275) isapplied as the measure of evaluation, and anti-knock properties can beevaluated by this octane value. In the present invention, a specificsubstance having an octane value of 80 or more can be defined as theanti-knock agent. Examples of the effective anti-knock agent includelead compounds such as tetraethyllead and tretramethyllead andcymantrene [Mn(C₅H₅)(CO)₃], and the employment of cymantrene or itsderivative is particularly preferable, because when it is used, bothworkability and stability are good, so that a very effective dyestuffthermal decomposition acceleration effect can be confirmed and theformation of the good pits can be confirmed.

A mixing ratio of the organic dyestuff for the recording to the pit-edgecontrol agent can be optimized by regulating the recording thresholdlevel of the organic dyestuff, but the proper ratio is 0.1-1,000 partsby weight of the pit-edge control agent, preferably 5-200 parts byweight to 100 parts by weight of the dyestuff. If the amount of thepit-edge control agent is less than this range, the functional effect ofthe present invention cannot be sufficiently exerted, and conversely ifit is more than the above-mentioned range, a recording sensitivitylargely declines and the additives tend to cohere and crystallizeunpractically.

Furthermore, the recording layer can usually be formed by dissolving theorganic dyestuff and the pit-edge control agent in a solvent to preparea coating solution, coating the transparent substrate with the coatingsolution, and then drying the same. In the formation process of therecording layer, coating methods such as spin coating method, a dipcoating method and a bar coat method can be used, but the spin coatingmethod is preferable because of being capable of providing the preciseand uniform layer.

In this case, it is preferable to select the solvent which can dissolvethe organic dyestuff and/or the added pit edge control agent but whichdoes not damage the substrate. Examples of the utilizable solventinclude aliphatic hydrocarbons such as n-heptane, n-octane, isoctane,cyclohexane, methylcyclohexane, ethylcyclohexane and1,2-dimethylcyclohexane; aromatic hydrocarbons such as toluene andxylene; halogen-containing hydrocarbons such as carbon tetrachloride andchloroform; alcohols such as methanol, ethanol and isopropanol; etherssuch as diethyl ether, dibutyl ether, isopropyl ether and dioxane;ethylene glycol ethers such as ethylene glycol methyl ether and ethyleneglycol ethyl ether; ketones such as cyclohexanone and methyl ethylketone; esters such as ethyl acetate and butyl acetate; and afluorine-containing alcohol such as 2,2,3,3-tetrafluoropropanol.Needless to say, these organic solvents may be used singly or in theform of a mixture of two or more thereof.

No particular restriction is put on the thickness of the organicdyestuff recording layer to which the pit-edge control agent has beenadded, but it is usually and properly in the range of from about 30 toabout 1,000 nm, more preferably and suitably from about 50 to about 300nm. If the thickness of the organic dyestuff recording layer is lessthan 30 nm, the release of heat to the metal reflective layer cannot beavoided and consequently, the sensitivity of the recording layerdecreases. Conversely, if it is more than 1000 nm, the decreases of thereflectance cannot be avoided owing to the absorption of the recordinglayer. The thickness outside this region can be also used in some cases.

Between the above-mentioned transparent substrate and the recordinglayer comprising the organic dyestuff layer, an intermediate layer maybe provided for the purposes of controlling the deformation of therecording pits toward the substrate side and obtaining adhesive strengththerebetween. This intermediate layer can be formed of a thermosettingorganic polymer, an Si polymer, a glass film or an inorganic film ofSiO₂, SnO₂ or AlN.

Furthermore, on the above-mentioned recording layer, a metallicreflective layer is formed. The material for this reflective layershould have a sufficiently high reflectance in the wavelength region ofthe used laser beam, and examples of such a usable material includemetals such as Au, Ag, Cu, Al, Cr and Ni. In addition, as the reflectivelayer, a multi-layer interference reflective layer can be used which isformed by alternately laminating a substance film having a lowrefractive index and an optically refractive substance film. Above all,Au and Al are preferable, because they permit the easy formation of thereflective layer having the high light reflectance. The reflective layerusually has a thickness of from 30 to 200 nm, and it can be formed by asputtering process, a vapor deposition process or an EB process.

Between this reflective layer and the recording layer, an intermediatelayer may be provided for the purposes of further improving thereflectance and improving adhesive strength between the recording layerand the reflective layer. This intermediate layer can be formed of apolymeric material such as a polycarbonate, methyl polymethacrylate,polysilane or siloxane, or an inorganic film of SiO₂, SnO₂ or AlN.

On the reflective layer, a protective layer is further provided. Noparticular restriction is put on the protective layer, so long as it canprotect the recording layer and the reflective layer. Examples of theusable material for the protective layer include polymeric materialssuch as a polycarbonate an acrylate, a polystyrene, vinyl chloride, anepoxy and a polyester. Above all, an ultraviolet-curable acrylic resinis optimum because of being capable of easily forming the protectivelayer. The thickness of the protective layer is preferably in the rangeof from 1 to 30 μm.

On the above-mentioned protective layer, one or more printing layers maybe further formed, the total thickness of the printing layers being inthe range of from 0.2 to 50 μm. This printing layer can usually beformed by a technique of screen printing or offset printing, and in thiscase, concave and convex portions of about 3 μm depth or less may beformed on purpose.

The appearance structure of the optical information recording medium ofthe present invention is not such as to be particularly described, butit may suitably take a single plate structure or a laminate structure(having recording layers on both sides) in compliance with a purpose.

According to the function of the present invention which is not beyondmere supposition, radical intermediates and the like are inevitablyproduced in the light/heat conversion step in the organic dyestuff layerat the time of the recording and the organic dyestuff decomposition stepwhich usually takes place after the conversion step, and variousexciting species of the thus produced radical intermediates and the likegive rise to a run-away reaction involving the violet generation of heatand in this step, the recording pits are formed. At this time, it can bepresumed that the recording layer and a substrate interface or ametallic reflective layer interface are exposed to a higher temperature,so that the behavior of the pit formation in the recording layer leadsto thermal deformation with the large volume change of the recordingfilm and the adjacent substrate interface or the adjacent reflectivelayer interface. At this time, the large thermal deformation isconsidered to bring about the deterioration of the pit-edge controlproperties, i.e., the deterioration of the deviation properties(particularly, 3T) and the decline of the jitter properties. It can bepresumed that the addition of the pit-edge agent, particularly, theaddition of the dye thermal decomposition accelerator lowers the dyethermal decomposition starting temperature at the time of the recording,so that the thermal deformation of the recording layer and itssurrounding can be decreased, whereby the characteristics of therecording layer can be improved. At this time, it is also important fortemperature control in the system to inhibit the heat generationattributable to the dyestuff decomposition, and therefore theabove-mentioned nitrocellulose system in which the generation of a largeamount of heat cannot be avoided at the time of the decomposition is notpreferable (however, if the content of the nitrocellulose is 5% or less,the nitrocellulose can be used together with the pit-edge agent whichcan be used in the present invention)

The reason why metallic compound, particularly, the organic metalliccompound functions as the effective dyestuff thermal decompositionaccelerator can be supposed to be that an electron transfer reactioncaused by the metallic compound acts effectively on a step of theformation and the extinction of active intermediate (e.g., radicals,ions or a triplet exciting state) at the time of the dyestuff thermaldecomposition by the oxidizing/reducing function of metallic atoms,metallic ions or a metallic compound itself contained in the compound,so that the thermal reaction is accelerated without involving anygeneration of a large amount of heat, and the decomposition propertiesof the organic dyestuff itself change. However, the detail of theabove-mentioned principle is obscure.

Now, the present invention will be described in detail in reference toexamples, but the scope of the present invention should not be limitedto these examples.

EXAMPLE 1

In 100 ml of ethylcyclohexane were dissolved 2.0 g of a phthalocyaninedyestuff represented by the formula

and synthesized in accordance with U.S. Pat. No. 5,124,067 as arecording dyestuff and 0.4 g of ferrocene (made by Tokyo Chemicals Co.,Ltd.) to prepare a coating solution. Afterward, a polycarbonatesubstrate provided with a spiral groove (pitch=1.6 μm, groove width=0.6μm and groove depth=0.18 m) and having an outer diameter of 120 mm and athickness of 1.2 mm was coated with the prepared coating solution byspin coating at 1,000 rpm to form a recording layer. Next, on thisrecording layer, Au was deposited as thick as 80 nm by a sputteringprocess to form a reflective layer. Furthermore, on this reflectivelayer was spin-coated an ultraviolet-setting resin SD-17 (made byDainippon Ink & Chemicals, Inc.), and the resin was then cured by UVirradiation to form a protective layer having a thickness of 6 μm.

The thus obtained CD-R medium was recorded (EFM recording) at a linearvelocity of 1.2 m/sec at 6.0 mW by an optical disk evaluation deviceDDU-1000 (made by Pulstech Industry Co., Ltd., laser wavelength=781 nmand NA=0.50), and then played back by an optical head carried on acommercial CD player. At this time, jitter, BLER (block error rate) andthe deviation of detection pits were measured by the use of a jittermeter (trade name LJM-1851, made by Leader Electronics Co., Ltd.), aCD-decoder (trade name DR 3552, made by KENWOOD Corp.) and a timinginterval analyzer (trade name TIA-175, made by ADC Co., Ltd.),respectively.

Furthermore, a TG analysis was carried out as follows: Each sample mixedwith a diethyl ether solution in the above-mentioned mixing ratio wasair-dried, and 10 mg of the resultant uniformly mixed powder was thenheated at a temperature rise rate of 10° C./min by means of multipurposethermal analyzer (trade name SSC 5200, made by Seiko ElectronicsIndustry Co., Ltd.) to obtain a weight loss curve.

The results of the evaluation are set forth in Table 1. The valuesshowing pit-edge controllability of 3T pit length and 3T land lengthwere evaluated to be s_(p)=38 ns (Δ_(p)=+2 ns, σ_(p)=18 ns) and s_(l)=54ns (Δ_(l)=−8 ns, σ₁=23 ns), respectively. These results indicate thatthe pit and the land were improved as much as 49 ns and 30 ns,respectively, as compared with a case where no ferrocene was added (seeComparative Example 1-1 given below). In this case, a measured dyestuffthermal decomposition starting temperature was 300° C., which meant thatthe temperature dropped about 50° C., as compared with the case where noferrocene was added. The signal properties of the medium obtained byforming a film from the mixture were also very excellent, and BLER<5 wasconfirmed.

In addition, a playback state was checked and scored 5 times per sampleby the use of a CD player (A) (trade name DP-8020, made by KenwoodCorp.), a CD player (B) (trade name CDP-C900, made by Sony Corp.) and aCD player (C) (XL-Z 521, made by JVC Co., Ltd.) and a CD player (D)(A725), made by Studer Co., Ltd.) As a result, as shown in Table 1, thecompatibility of these samples with the above-mentioned CD-players wasvery excellent.

COMPARATIVE EXAMPLE 1-1

The same procedure as in Example 1 was carried out except that anyferrocene was not added, to prepare a medium, and evaluation was thenmade in the same manner as in Example 1. The results of the evaluationare set forth in Table 1. The measured values of s_(p)=87 ns (Δ_(p)=+35ns, σ_(p=)26 ns) and s_(l)=84 ns (Δ_(l)=−12 ns, σ_(l)36 ns) were higheras compared with those of Example 1, and a measured dyestuffdecomposition starting temperature was 350° C. BLER was as high as 200,which meant that it was worse as compared with that of Example 1. It wasalso confirmed by some CD players that playback was defective.

COMPARATIVE EXAMPLE 1-2

The same procedure as in Example 1 was carried out except that ferrocenewas replaced with CBr₄, to prepare a medium, and evaluation was thenmade in the same manner as in Example 1. The results of the evaluationare set forth in Table 1. The values of s_(p)=87 ns (Δ_(p)=+35 ns,σ_(p)=26 ns) and s_(l)=81 ns (Δ_(l)=−13 ns, σ_(l)=34 ns) were evaluated,and a measured dyestuff decomposition starting temperature was 360° C.BLER was as high as 250, which meant that it was worse as compared withthat of Example 1 and the improvement of characteristics was notobserved at all. It was also confirmed by CD layers that defectiveplayback often occurred.

EXAMPLE 2

In 100 ml of dibutyl ether were dissolved 2.0 g of a brominatedphthalocyanine dyestuff having the structural formula:

and synthesized in accordance with U.S. Pat. No. 5,124,067 as arecording dyestuff and 0.4 g of ferrocene to prepare a coating solution.Afterward, the same substrate as in Example 1 was spin-coated with thecoating solution to form a film. Next, a TG analysis and the signalevaluation of the resultant CD-R medium were carried out in the samemanner as in Example 1 (recording power=6.0 mW). The results of theevaluation are set forth in Table 1.

A decomposition starting temperature was 260° C., and the values ofs_(p)=38 ns (Δ_(p)=−2 ns, σ_(p)=18 ns) and s_(l)=50 ns (Δ_(l)=−10 ns,σ_(l)=20 ns) were evaluated. BLER <5 which meant very excellentproperties was obtained. Furthermore, on each type of the CD players,stable playback was confirmed.

COMPARATIVE EXAMPLE 2

The same procedure as in Example 2 was carried out except that anyferrocene was not added, to prepare a medium, and evaluation was thenmade in the same manner as in Example 1. The results of the evaluationare set forth in Table 1. The measured values of s_(p)=68 ns ands_(l)=74 ns meant much power characteristics as compared with those ofExample 2, and it was also confirmed by some of the CD players thatplayback was defective.

EXAMPLE 3-1

In 100 ml of ethylcyclohexane were dissolved 2.0 g of a brominatedphthalocyanine dyestuff having the structural formula:

and synthesized in accordance with U.S. Pat. No. 5,124,067 as arecording dyestuff and 0.4 g of ferrocene to prepare a coating solution.Afterward, the same substrate as in Example 1 was spin-coated with thecoating solution at 1,000 rpm to form a film. Next, a TG analysis andthe signal evaluation of the resultant CD-R medium was carried out inthe same manner as in Example 1 (recording power=5.5 mW). The results ofthe evaluation are set forth in Table 1.

In this case, a measured dyestuff thermal decomposition startingtemperature was 255° C., which meant that the temperature dropped about40° C., as compared with the case where no ferrocene was added. Thesignal properties of the medium obtained by forming a film from themixture were s_(p)=45 ns, s_(l)=50 and BLER <5, where were indicative ofgood characteristics. In addition, the compatibility of the medium witheach type of the CD-players were very excellent.

EXAMPLE 3-2

The same experiment as in Example 3-1 was carried out except thatferrocene was replaced with benzoylferrocene (made by Aldrich Co., Ltd.)and the same dyestuff as in Example 13-1 and benzoylferrocene were mixedin a weight ratio of 5:1 in accordance with the same prescription as inExample 3-1 to form a film. The results of the evaluation are set forthin Table 1.

Pit edge controllability was evaluated to be s_(p)=49 ns (Δ_(p)=−7 ns,σ_(p)=21 ns) and s_(l)=50 ns (Δ_(l)=−10 ns, σ_(l)=−20 ns). A dyestuffthermal decomposition starting temperature was 235° C. (a drop of 60°C.) by which it was confirmed that the decomposition was remarkablyaccelerated, and the signal properties of the medium were also good,BLER<5. In addition, the compatibility of the medium with each type ofthe CD-players were very excellent.

EXAMPLE 3-3

The same experiment as in Example 3-1 was carried out except thatferrocene was replaced with 1,1′-dimethylferrocene (made by TokyoChemicals Co., Ltd.) and the same dyestuff as in Example 3-1 and1,1′-dimethylferrocene were mixed in a weight ratio of 5:1 in accordancewith the same prescription as in Example 3-1 to form a film. The resultsof the evaluation are set forth in Table 1.

A dyestuff thermal decomposition starting temperature was confirmed tobe 240° C. (a drop of 55° C.), and signal properties of the resultantmedium were s_(p)=38 ns, s_(b =48) ns and BLER<5, which was indicativeof good characteristics. In addition, the compatibility of the mediumwith each type of the CD-players was also very excellent.

EXAMPLE 3-4

The same experiment as in Example 3-1 was carried out except thatferrocene was replaced with n-butylferrocene (made by Tokyo ChemicalsCo., Ltd) and the same dyestuff as in Example 3-1 and n-butylferrocenewere mixed in a weight ratio of 5:1 in accordance with the sameprescription as in Example 3-1 to form a film. The results of theevaluation are set forth in Table 1.

A dyestuff thermal decomposition starting temperature was confirmed tobe 250° C. (a drop of 45° C.), and pit-edge control properties were goodand the signal properties of the resultant medium were very excellent,BLER<5. In addition, the compatibility of the medium with each type ofthe CD-players was also very excellent.

EXAMPLE 3-5

The same experiment as in Example 3-1 was carried out except thatferrocene was replaced with cyclohexenylferrocene (made by TokyoChemicals Co., Ltd.) and the same dyestuff as in Example 3-1 andcyclohexenylferrocene were mixed in a weight ratio of 5:1 in accordancewith the same prescription as in Example 3-1 to form a film. The resultsof the evaluation are set forth in Table 1.

The frop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant medium were very excellent, BLER<5. Inadditions the compatibility of the medium with each type of theCD-players was also very excellent.

EXAMPLE 3-6

The same experiment as in Example 3-1 was carried out except thatferrocene was replaced with vinylferrocene (made by Tokyo Chemicals Co.,Ltd.) and the same dyestuff as in Example 3-1 and vinylferrocene weremixed in a weight ratio of 5:1 in accordance with the same prescriptionas in Example 3-1 to form a film. The results of the evaluation are setforth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant media were very excellent, BLER<5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

COMPARATIVE EXAMPLE 3-1

The same procedure as in Example 3-1 was carried out except that anyferrocene was not added, to prepare a medium, and evaluation was thenmade in the same manner as in Example 3-1. The results of the evaluationare set forth in Table 1.

A dyestuff thermal decomposition starting temperature was confirmed tobe 295° C., and pit-edge controllability was evaluated to be s_(p)=76 ns(Δ_(p)=+30 ns, σ_(p)=23 ns) and s_(l)=79 ns (Δ_(l)=−15 ns, σ_(l)=32 ns),and BLER was not good, 50. It was also confirmed by one CD player thatplayback was defective.

COMPARATIVE EXAMPLE 3-2

The same experience as in Example 3-1 was carried out except thatferrocene was replaced with transtibene (made by Tokyo Chemicals Co.,Ltd.) and the same dyestuff as in Example 3-1 and transstilbene weremixed in a weight ratio of 5:1 in accordance with the same prescriptionas in Example 3-1 to form a film. The results of the evaluation are setforth in Table 1.

A dyestuff thermal decomposition starting temperature was 305° C., andpit-edge controllability was also bad. In addition, it was alsoconfirmed by all the CD players that playback was defective.

EXAMPLE 4-1

In 100 ml of a mixed solvent of ethylcyclohexane and isopropanol (in avolume ratio of 100:5) were dissolved 2.0 g of a brominatedphthalocyanine dyestuff used in Example 3-1 as a recording dyestuff and0.3 g of acetylacetonato iron complex [Fe(acac)₃, made by TokyoChemicals Co., Ltd.) to prepare a coating solution. Afterward, the samesubstrate as in Example 1 was spin-coated with the coating solution at800 rpm to form a film. Next, a TG analysis and the signal evaluation ofthe resultant CD-R medium was carried out in the same manner as inExample 1 (recording power=5.0 mW). The results of the evaluation areset forth in Table 1.

A measured dyestuff thermal decomposition starting temperature was 250°C. (a drop of 45° C.). The pit-edge controllability of the mediumobtained by forming the film from the above-mentioned mixture wasevaluated to be s_(p)=57 ns (Δ_(p)=+15 ns, σ_(p)=21 ns) and s_(l)=56 ns(Δ_(l)=−10 ns, σ_(l)=23 ns) and BLER was 5, and these values wereindicative of good characteristics. In addition, the compatibility ofthe media with each type of the CD-players were also excellent.

EXAMPLE 4-2

The same experiment as in Example 4-1 was carried out except thatacetylacetonato iron complex was replaced with acetylacetonato chromiumcomplex [Cr(acac)₃, made by Tokyo Chemicals Co., Ltd.)] and the samedyestuff as in Example 3-1 and acetylacetonato chromium complex weremixed in a weight ratio of 7.5:1 in accordance with the sameprescription as in Example 4-1 to form a film. The results of theevaluation are set forth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant medium were also very excellent, BLER <5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

EXAMPLE 4-3

The same experiment as in Example 4-1 was carried out except thatacetylacetonato iron complex was replaced with acetylacetonato cobaltcomplex [Co(acac)₃, made by Tokyo Chemicals Co., Ltd.)] and the samedyestuff as in Example 3-1 and acetylacetonato cobalt complex were mixedin a weight ratio of 7.5:1 in accordance with the same prescription asin Example 4-1 to form a film. The results of the evaluation are setforth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant medium were also very excellent, BLER<5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

EXAMPLE 4-4

The same experiment as in Example 4-1 was carried out except thatacetylacetonato iron complex was replaced with acetylacetonato vanadiumcomplex [V(acac)₃, made by Tokyo Chemicals Co., Ltd.)] and the samedyestuff as in Example 3-1 and acetylacetonato vanadium complex weremixed in a weight ratio of 7.5:1 in accordance with the sameprescription as in Example 4-1 to form a film. The results of theevaluation are set forth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit edge control properties were confirmed, and the signalproperties of the resultant medium were also very excellent, BLER<5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

COMPARATIVE EXAMPLE 4

The same experiment as in Example 4-1 was carried out except thatacetylacetonato iron complex was replaced with acetylacetone (made byTokyo Chemicals Co., Ltd.) and the same dyestuff as in Example 3-1 andacetylacetone were mixed in a weight ratio of 7.5:1 in accordance withthe same prescription as in Example 4-1 to form a film. The results ofthe evaluation are set forth in Table 1.

A dyestuff thermal decomposition starting temperature was 315° C., andpit-edge controllability was also bad.

EXAMPLE 5

In 100 ml of butyl ether were dissolved 2.0 g of a brominatedphthalocyanine dyestuff used in Example 3-1 as a recording dyestuff and0.2 g of cymantrene [Mn(C₅H₅) (CO)₃, made by Aldrich Co., Ltd.] toprepare a coating solution in a weight ratio of 10:1. Afterward, thesame substrate as in Example 1 was spin-coated with the coating solutionat 800 rpm to form a film. Next, a TG analysis and the signal evaluationof the resultant CD-R medium were carried out in the same manner as inExample 1 (recording power=5.0 mW). The results of the evaluation areset forth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant medium were also very excellent, BLER<5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

EXAMPLE 6

The same experiment as in Example 5 was carried out except thatcymantrene was replaced with naphthenic acid iron (made by TokyoChemicals Co., Ltd.) and the same dyestuff as in Example 3-1 andnaphthenic acid iron were mixed in a weight ratio of 10:1 in accordancewith the same prescription as in Example 5 to form a film. The resultsof the evaluation are set forth in Table 1.

The drop of a dyestuff thermal decomposition starting temperature andgood pit-edge control properties were confirmed, and the signalproperties of the resultant medium were also very excellent, BLER<5. Inaddition, the compatibility of the medium with each type of theCD-players was also very excellent.

TABLE 1 T_(die) S_(P) s₂ (° C.) (nm) (cm) BLER Example 1 295 38 54 <5Comp. Ex. 1-1 350 87 84 200  Comp. Ex. 1-2 360 87 81 250  Example 2 26038 50 <5 Comp. Ex. 2 305 68 74 20 Example 3-1 255 45 50 <5 Example 3-2235 49 49 <5 Example 3-3 240 38 48 <5 Example 3-4 250 40 47 <5 Example3-5 250 45 47 <5 Example 3-6 240 50 52 <5 Comp. Ex. 3-1 295 76 79 50Comp. Ex. 3-2 305 93 84 860  Example 4-1 250 57 56 10 Example 4-2 255 4748 <5 Example 4-3 260 46 51 <5 Example 4-4 250 40 47 <5 Comp. Ex. 4 30088 78 500  Example 5 250 49 55 <5 Example 6 270 58 66 10 Playability A BC D Example 1 5 5 5 5 Comp. Ex. 1-1 0 5 1 0 Comp. Ex. 1-2 0 5 0 0Example 2 5 5 5 5 Comp. Ex. 2 5 5 5 0 Example 3-1 5 5 5 5 Example 3-2 55 5 5 Example 3-3 5 5 5 5 Example 3-4 5 5 5 5 Example 3-5 5 5 5 5Example 3-6 5 5 5 5 Comp. Ex. 3-1 5 5 5 0 Comp. Ex. 3-2 0 0 0 0 Example4-1 5 5 5 5 Example 4-2 5 5 5 5 Example 4-3 5 5 5 5 Example 4-4 5 5 5 5Comp. Ex. 4 0 1 0 0 Example 5 5 5 5 5 Example 6 5 5 5 5

In Table 1, the dyestuff thermal decomposition starting temperature(T_(dis)) obtained by the TG analysis and the evaluation results of thepit-edge controllability s_(p) and s_(l) of the 3T pits and lands as thesignal evaluation results of the resultant CD-R media are described.Furthermore, in this table, there are shown the values of the blockerror rates (BLER) which are the indexes of the compatibility with thecommercial CD players, and the evaluation results of the playability ofthe media on the above-mentioned several commercial CD players (A, B, Cand D). The playability has been evaluated by scoring the confirmednumber of the normal operations of the media in the case that a playbacktest has been carried out 5 times on each CD player.

As is apparent from Table 1, there is the tendency that the dyestuffthermal decomposition starting temperature can be dropped by adding thepit-edge control agent, i.e., the dyestuff thermal decompositionaccelerator, and thus the index of the pit-edge controllability can bedropped, so that the signal properties of the CD-R media can be largelyimproved.

From Examples 1, 2, 3-1 to 3-6 and Comparative Examples 1-1, 1-2, 2, 3-1and 3-2, the improvement of the pit-edge controllability by adding ametallocene and its derivative has been confirmed together with theremarkable drop of the thermal decomposition starting temperatures ofthe recording dyestuffs, and it is also shown that BLER of the CD-Rmedia comprising the system is sufficiently low. In addition, thecompatibility with each type of the commercial CD players has also beenconfirmed.

From Examples 4-1 to 4-4 and Comparative Example 4, the effect due tothe addition of β-diketonato metal complex has been confirmed.

Furthermore, from Example 5, the effect of cymanthrene for remarkablyshowing anti-knock properties has been certified, and in Example 6, thegood properties of the iron-containing metallic compound has beenconfirmed.

As described above, the deviation properties and the jitter propertiescan be remarkably improved by adding the pit-edge control agent, aboveall, the dyestuff thermal decomposition accelerator for the formed pitsto the recording film comprising the recording dyestuff, whereby theCD-R media having a low error rate and good recording properties can beprovided. In consequence, the stable compatibility with the commercialCD players can be secured.

1. A composition for a pit-forming optical information recording mediumwhich comprises an organic dyestuff comprising a phthalocyanine compoundand an effective amount for pit edge control of a pit-edge controlagent, wherein said pit-edge control agent is a thermal decompositionaccelerator for the dyestuff, is a metallic compound, has substantiallyno absorption at the wavelength of a recording laser beam, and issoluble in a solvent for the organic dyestuff and wherein the amount ofsaid pit-edge control agent is in the range of from 0.1 to 1,000 partsby weight based on 100 parts by weight of the organic dyestuff andwherein the pit-edge control agent decreases the thermal decompositionstarting temperature of the organic dyestuff at least 10° C.
 2. Thecomposition for an optical information recording medium according toclaim 1 wherein said metallic compound is a metallocene or itsderivative.
 3. The composition for an optical information recordingmedium according to claim 1 wherein said metallic compound is aβ-diketonato metal complex represented by formula (1):

wherein each of the substituents X, Y and Z is independently a hydrogenatom, a halogen atom, R¹, OR², SR³, COOR⁴, COONR⁵R⁶, SiR⁷R⁸R⁹ orNR¹⁰R¹¹, and M^(n+) is a metal having a valency of n (wherein R¹ is anunsubstituted or substituted alkyl group, aryl group or unsaturatedalkyl group, and each of R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, R¹⁰ or R¹¹ is ahydrogen atom, an unsubstituted or substituted alkyl group, aryl groupor unsaturated alkyl group).
 4. The composition for an opticalinformation recording medium according to claim 1 wherein said metalliccompound is an anti-knocking agent.
 5. The composition for an opticalinformation recording medium according to claim 1 wherein said organicdyestuff is a phthalocyanine compound.
 6. The composition for an opticalinformation recording medium according to claim 5 wherein saidphthalocyanine compound is a halogenated phthalocyanine.
 7. A method forpreparing an optical information recording medium which comprises thesteps of: dissolving the composition of claim 1 in a solvent to form asolution, and coating the thus obtained solution on a transparentsubstrate, thereby forming a recording layer comprising the organicdyestuff and the pit-edge control agent.
 8. A composition for apit-forming optical information recording medium which comprises anorganic dyestuff comprising a phthalocyanine compound and an effectiveamount for pit edge control of a pit-edge control agent, wherein saidpit-edge control agent is a thermal decomposition accelerator for thedyestuff, is an iron metallic compound, has substantially no absorptionat the wavelength of a recording laser beam, and is soluble in a solventfor the organic dyestuff and wherein the amount of said pit-edge controlagent in said composition is in the range of from 0.1 to 1,000 parts byweight based on 100 parts by weight of the organic dyestuff and whereinthe pit-edge control agent decreases the thermal decomposition startingtemperature of the phthalocyanine compound at least 10° C.
 9. Thecomposition for an optical information recording medium according toclaim 8 wherein the pit-edge control agent decreases the thermaldecomposition starting temperature of the phthalocyanine compound atleast 25° C.
 10. The composition for an optical information recordingmedium according to claim 8 wherein the phthalocyanine compound and thepit-edge control agent are physically or chemically interacted.
 11. Acomposition suitable for forming a recording layer in a pit-formingoptical information recording medium which comprises an organic dyestuffcomprising a phthalocyanine compound and an effective amount for pitedge control of a pit-edge control agent selected from the groupconsisting of ferrocene and derivatives of ferrocene, wherein saidpit-edge control agent is a thermal decomposition accelerator for thedyestuff, has substantially no absorption at the wavelength of arecording laser beam, and is soluble in a solvent for the organicdyestuff and wherein the amount of said pit-edge control agent in saidcomposition is in the range of from 0.1 to 1,000 parts by weight basedon 100 parts by weight of the organic dyestuff and wherein the pit-edgecontrol agent decreases the thermal decomposition starting temperatureof the organic dyestuff at least 10° C.
 12. The composition suitable forforming a recording layer in an optical information recording mediumaccording to claim 11 wherein the pit-edge control agent decreases thethermal decomposition starting temperature of the organic dyestuff atleast 25° C.
 13. The composition suitable for forming a recording layerin an optical information recording medium according to claim 11 whereinthe derivatives of ferrocene have a substituent selected from the groupconsisting of alkyl groups having 1-10 carbon atoms, acyl groups having2-10 carbon atoms, aryl groups having 6-10 carbon atoms, aryloyl groupshaving 7-10 carbon atoms, aldehyde groups having 1-10 carbon atoms,carboxyl groups having 1-10 carbon atoms, alkoxy groups having 1-10carbon atoms, amino groups having 0-10 carbon atoms, a hydroxyl group,halogen atoms and alkenyl groups having 2-10 carbon atoms.
 14. Thecomposition suitable for forming a recording layer in an opticalinformation recording medium according to claim 11 wherein thederivatives of ferrocene have a substituent selected from the groupconsisting of alkyl groups having 1-10 carbon atoms, acyl groups having2-10 carbon atoms and a benzoyl group.
 15. The composition suitable forforming a recording layer in an optical information recording mediumaccording to claim 11 wherein the pit-edge control agent is ferrocene.16. The composition suitable for forming a recording layer in an opticalinformation recording medium according to claim 11 wherein the organicdyestuff and the pit-edge control agent are physically or chemicallyinteracted.
 17. The composition for an optical information recordingmedium according to claim 1 wherein the pit-edge control agent decreasesthe thermal decomposition starting temperature of the organic dyestuffat least 25° C.
 18. The composition for an optical information recordingmedium according to claim 1 wherein the organic dyestuff and thepit-edge control agent are physically or chemically interacted.
 19. Acomposition which is in the form of a solution and which is suitable forforming a recording layer in a pit-forming optical information recordingmedium comprising a solvent having dissolved therein an organic dyestuffcomprising a phthalocyanine compound and an effective amount for pitedge control of a pit-edge control agent, wherein said pit-edge controlagent is a thermal decomposition accelerator for the dyestuff, is ametallic compound, and has substantially no absorption at the wavelengthof a recording laser beam, and wherein the amount of said pit-edgecontrol agent in said composition is in the range of from 0.1 to 1,000parts by weight based on 100 parts by weight of the organic dyestuff andwherein the pit-edge control agent decreases the thermal decompositionstarting temperature of the organic dyestuff at least 10° C.
 20. Thecomposition according to claim 19 wherein the pit-edge control agentdecreases the thermal decomposition starting temperature of the organicdyestuff at least 25° C.
 21. The composition according to claim 19wherein the pit control agent is selected from the group consisting offerrocene and derivatives of ferrocene.
 22. The composition according toclaim 21 wherein the derivatives of ferrocene have a substituentselected from the group consisting of alkyl groups having 1-10 carbonatoms, acyl groups having 2-10 carbon atoms, aryl groups having 6-10carbon atoms, aryloyl groups having 7-10 carbon atoms, aldehyde groupshaving 1-10 carbon atoms, carboxyl groups having 1-10 carbon atoms,alkoxy groups having 1-10 carbon atoms, amino groups having 0-10 carbonatoms, a hydroxyl group, halogen atoms and alkenyl groups having 2-10carbon atoms.
 23. The composition according to claim 21 wherein thederivatives of ferrocene have a substituent selected from the groupconsisting of alkyl groups having 1-10 carbon atoms, acyl groups having2-10 carbon atoms and a benzoyl group.
 24. The composition according toclaim 19 wherein the pit-edge control agent is ferrocene.
 25. Thecomposition according to claim 19 wherein the organic dyestuff and thepit-edge control agent are physically or chemically interacted.
 26. Amethod for preparing an optical information recording medium whichcomprises the steps of: forming a solution comprised of a solvent havingdissolved therein an organic dyestuff comprising a phthalocyaninecompound and a pit-edge control agent wherein said pit-edge controlagent is a thermal decomposition accelerator for the dyestuff, is ametallic compound, and has substantially no absorption at the wavelengthof a recording laser beam, wherein the amount of said pit-edge controlagent in said composition is in the range of from 0.1 to 1,000 parts byweight based on 100 parts by weight of the organic dyestuff and whereinthe pit-edge control agent decreases the thermal decomposition startingtemperature of the organic dyestuff at least 10° C., and coating thethus obtained solution on a substrate, thereby forming a recording layercomprising the organic dyestuff and the pit-edge control agent.
 27. Themethod according to claim 26 wherein the pit-edge control agentdecreases the thermal decomposition starting temperature of the organicdyestuff at least 25° C.
 28. The method according to claim 26 whereinthe pit-edge control agent is selected from the group consisting offerrocene and derivatives of ferrocene.
 29. The method according toclaim 28 wherein the derivatives of ferrocene have a substituentselected from the group consisting of alkyl groups having 1-10 carbonatoms, acyl groups having 2-10 carbon atoms, aryl groups having 6-10carbon atoms, aryloyl groups having 7-10 carbon atoms, aldehyde groupshaving 1-10 carbon atoms, carboxyl groups having 1-10 carbon atoms,alkoxy groups having 1-10 carbon atoms, amino groups having 0-10 carbonatoms, a hydroxyl group, halogen atoms and alkenyl groups having 2-10carbon atoms.
 30. The method according to claim 28 wherein thederivatives of ferrocene have a substituent selected from the groupconsisting of alkyl groups having 1-10 carbon atoms, acyl groups having2-10 carbon atoms and a benzoyl group.
 31. The method according to claim26 wherein the pit-edge control agent is ferrocene.
 32. The method ofclaim 26 wherein the organic dyestuff and the pit-edge control agent arephysically or chemically interacted.